Prostaglandins appear to play a highly important role in the regulation of cellular metabolism. Although they are considered to be mediators of inflammation, little is known regarding their effect on particular cartilage on rheumatoid arthritis or osteoarthritis. In addition, there is little known regarding the role of endogenous prostaglandins in articular, epiphyseal or neoplastic cartilage, but it is possible to speculate that they may be important regulators of metabolic processes. The proposed research will use biochemical and radioisotopic metabolic techniques to: determine the nature of the prostaglandins secreted by rheumatoid synovium, chondrosarcoma, and epiphyseal cartilage and the factors which influence their synthesis; define the effect of prostaglandins and intermediates on metabolism of articular cartilage; evaluate the possiblity that cartilage synthesizes prostaglandins and that these function as endogenous components of a cell regulatory mechanism.